Britain's taxpayers are destined to finance an increasing amount of "faith-based welfare". Both Labour and Conservatives are committed to handing over large tracts of social care to religious bodies – with accompanying funding – and there seems to be little restraint proposed to stop these groups using the money in a discriminatory way.

In the US, the White House Office of Faith-Based and Neighbourhood Partnerships was set up, amid great controversy, by George W Bush. At the time, there were bitter arguments about its legality under America's constitutional separation of church and state. There were suspicions that it was, in fact, simply a means for Bush to buy the support of religious leaders.

To assuage this criticism, conditions were attached to the provision of tax dollars. The money was not be used for proselytising, all religious activities were to be kept separate from the welfare element and there was to be no discrimination in the provision of services. But since then, there has been a succession of court cases illustrating that many religious groups do not observe these restrictions.

In a campaign speech on faith-based initiatives in July 2008, Barack Obama made clear that he would continue with the programme but said: " … if you get a federal grant, you can't use that grant money to proselytise to the people you help and you can't discriminate against them – or against the people you hire – on the basis of their religion."

However, since coming to office, and despite pressure he has failed to keep that pledge, and discrimination by religious groups continues.

The National Secular Society has been pressing the British government not to make the same mistakes and to learn from the American experience. We have demanded the introduction of some kind of similar statutory safeguards.

When Hazel Blears was community secretary she came up with a so-called Charter of Excellence (which was based on the Faithworks Charter). In a speech to the Evangelical Alliance she said that the charter would ensure that those groups accessing public money to run services would not use it to proselytise or to deny services on religious grounds, but scandalously required no equivalent condition on employment.

The government has now dropped the charter, I suspect because religious groups would not accept even these minimal limitations.

The problem with the proposed charter was that it would have been merely a voluntary code. Those religious groups that are already committed to fairness and non-discrimination would have had no problem with it, but the very groups that are most likely to want to discriminate – the evangelicals and the fundamentalists – would have refused to sign up to it. Another danger was that it would have been an undeserved and unpoliced "trophy" that would have been waved in the face of those local authorities that were reluctant to fund such groups.

What we would like to see is a much tougher legal requirement on groups not to use public money which is meant for social services for the promotion of their faith. The law must forbid them from using taxpayers' money not only to discriminate against their service users but also their staff on grounds of religion or sexuality. This is an unpardonable omission from the current equality bill which the government still has time to rectify.

We also urgently need to elimination the discrimination that is enshrined in law for faith schools. Here we have state-funded schools that are permitted to demand that their headteacher is of a particular religion and to sack staff if they fail to abide by the relevant religious tenets even outside school. However exemplary at their job, atheist or unmarried cohabiting teachers could be fired by a zealous headteacher.

Many religious groups have big problems dealing with gay people and non-believers and don't like to think of them on their payroll and it is for this reason that the government really must think hard – and fast – about how it is going to ensure that welfare services, traditionally provided by secular local authorities, do not attain the same reputation for unjust practices and bigotry that many of our "faith schools" already have.